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What Is a Delayed Allergic Reaction?

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  • Written By: Mary McMahon
  • Edited By: Shereen Skola
  • Last Modified Date: 15 August 2014
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A delayed allergic reaction typically begins between two and three days after exposure to an antigen, rather than almost immediately. Such reactions can be observed with a number of allergens and can be tricky to diagnose and treat because doctors usually assume allergies are related to recent exposures. Some delays take even longer; in a condition called serum sickness, it may take a week or more for the patient to react to foreign proteins falsely tagged as dangerous by the body.

Patients experience a delayed allergic reaction when the response to an allergen is mediated by the leukocytes, the white blood cells. This secondary cellular response takes several days to manifest itself because the T cells and macrophages need time to start working. As a result, the patient might be exposed to an allergen and feel fine until several days later, when symptoms like rash and difficulty breathing develop. The intensity of the reaction can depend on immune health and the allergen.

Some drugs are associated with delayed allergic reaction, like certain antibiotics and antiserums used in treatment of disease. Patients who experience severe allergy symptoms and go to the doctor should make sure to cover their recent medical history. This includes not just what they ate, drank, or were exposed to in the last hours, but over the last week. The doctor might spot something that could have caused a delayed reaction and might be the cause of the symptoms.

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It is possible to use allergy testing to check for a delayed allergic reaction. In this testing, the patient receives a series of challenges, exposures to an antigen through pricks or scratches in the skin. The doctor notes which challenges result in a response, and how long it takes for signs of a response to develop. Such testing can carry some risks for patients with extreme allergies, but the exposure is so minimal that the benefits of the testing in a controlled environment may outweigh the risks.

Recurrent allergies that do not seem to respond to testing or treatment could be an example of a delayed allergic reaction. The patient might be taking reasonable steps to identify allergens under the assumption that any reaction would occur immediately after exposure. Meanwhile, the culprit behind the delayed reaction might not be fingered because it doesn't cause the instantaneous response. These patients may need to meet with an allergy specialist to go over their history and explore testing options to find out what is making them sick.

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anon953824
Post 4

I was diagnosed with multiple (over 20) both immediate and delayed allergies over 10 years ago. What I know to be true from over 10 years of experience: doctors don't know anything about our bodies and brains. They know nothing, zero, nada.

The first thing I would like to say is food allergy symptoms can not only occur in 0 to 72 hours from eating the food. They can also cause foods that one isn't particularly allergic to, to cause more severe symptoms during the next week. "Got a reaction 24h after eating parsley", "the next week strawberries are going to itch my throat a lot more than usual".

The second thing is, the symptoms can change as you grow older. In my case, they began as 10-60 minute diarrhea episodes and shock (nausea, fast and irregular heartbeat). Now, 10 years later they can last from 15 minutes to six hours, no diarrhea, but all the symptoms of shock plus far more mental aspects of shock (nonspecific/overal feelings of fear, pain, confusion etc). To describe the feeling of fear shock causes, I say it's like when you were little, you were scared by dark and your imagination caused you to be even more scared. It feels like that, only this time you are consciously aware that there is no reason to be fearful, but your body still fears.

The third thing is, food allergy can affect hormone balance. I am a man who has a high sex drive, yet sometimes among other allergy symptoms, I can temporarily lose almost all my sex drive, I will not get the morning erections and so on. What is strange is, this sort of thing is usually caused by stress and/or depression, but when it is allergy related, there doesn't need to be any stress or depression.

The fourth thing is, the amount of allergy causing food often has no relation whatsoever to the severity of the symptoms.

Fifth, there is medicine that will help allergy symptoms; you just don't think of it as medicine. A high amount of caffeine can noticeably help the symptoms, including pollen allergy symptoms, and by high I mean half a liter (16 oz) of Coke. And even eating something like a sandwich, even when you don't feel like you could eat, will help the symptoms. I think the reason is, your brain's thinking goes like this: "something is seriously wrong.. wait he/she is eating, false alarm, move on".

Sixth, the symptoms may not include any stomach ache and/or airways tightening, but still there can be breathing difficulties and problems in the circulatory system.

Last, one can live a normal life with allergies like these. you just have to avoid the problematic foods, and when symptoms occur, remind yourself that it is just an allergy and there is no need to worry about things even when your body says you should worry about things.

croydon
Post 3

If you aren't sure what's causing your allergies it's definitely a good idea to go and see a specialist. There is a whole world of difference between living with an allergy and living without suffering from it all the time.

Staying away from the allergen can be difficult, but it's still better than the alternative.

lluviaporos
Post 2

@Ana1234 - It's particularly bad for food allergens because they can be much harder to test for than some of the the other kinds. And with the delay, I think the only real way to tell what is causing the problems would be an exclusion diet.

I've had to do one of those myself and it was a pain in the butt, let me tell you. Because you really have to go off of almost everything for weeks so that it will clear your system, otherwise you might contaminate the results. And most modern foods seem to have a little bit of everything mixed in. I certainly don't envy people who are allergic to several things.

Ana1234
Post 1

This must be so very scary and frustrating for parents with allergic kids. It's hard enough sometimes to figure out what someone is allergic to, even when they have a normal allergic reaction right after exposure.

The fact that any reaction could also be a delayed reaction would really make me paranoid about paying attention to each little thing they brush past or put in their mouths.

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